Reproducer



April 1945. K. J. GERMESHAUSEN 2,373,675

REPRODUCER Filed July so, 1941 2 Sheets-Sheet 1 April 1 K. J. GERMESHAUSEN 2,373,676

REPRODUCER Filed July 30, 1941 2 SheetsShet 2 i with the damper removed, of the vibrator-translator of insulating mater Patented Apr. 17, 1945 U NITED STATES PATENT OFFICE 9 Claims.

This application relates to a reproducer, and

more particularly to an improved reproducer and associated circuits for electrically reproducing recorded mechanical variations.

One feature of this invention is that it provides improved record reproducing apparatus; another feature of this invention is that it provides a strain sensitive coated vibrator-translator and associated circuits developing greater voltage variations for a given mechanical movement; another feature of this invention is that it almost completely balances out undesired harmonic distortion;-yet another feature of this invention is that it enables the vibrator-translator coating resistance included between the poles of the source of voltage to be much higher than heretofore; a still further feature of this invention is that it enables push-pull operation without a coupling transformer, other features and advantages of this invention will be apparent from the following specification and the drawings, in

which:

Figure 1 is a circuit diagram of reproducing apparatus embodying my invention; Figure 2 is a side elevational view of a vibrator-translator element adapted to be used in the circuit of Figure 1; Figure 3 is a top plan view of the element shown in Figure 2; Figure 1 i a side elevational view, from the other side, of the element shown in Figure 2; Figure 5 is a front elevational view, same element; Figure 6 is a circuit diagram of a modification of my invention; Figure 7 is a side elevational view of a vibrator-translator element adapted to be used in the circuit shown in Figure 6, a side elevational view of the other element shown in Figure 7; and skeleton view of the coatings and ri le same element, to more clearly show ment and connection of these pa I have found that a considerable in record reproduction is obtained by i modulus of elasticity, as Celluloid or i with a coating or ayer on at least 0 material in igh resistance anc strain, as a sprayeol-on coating of graphite. Such an element is ada, one end rigid v mounted in a tone other end. .d by the engagemei rigidly mou with the 1 reproduced, of the variation in t.. Mar 1 in the coaii thus variation in its resistance. By a voltage across the length of the re. eating variation of its impedance varies the voltage drop, this voltage variation faithfully following the mechanical variations in the record and being adapted to be supplied to the grid of the first tube of an amplifier, to be highly amplified and. supplied to a speaker. Such. reproducing apparatus has been more fully described in my copending application, Serial No. 340,156, filed June 12, 1940, and the general advantages and basic principles of such reproducing apparatus will not be further described here except as they may be necessary to enable clear understanding of the present improvements. This application is a continuation-in-part of my aforesaid earlier application.

Inasmuch as the basic ideas and features of such reproducing apparatus have been claimed in my abovementioned earlier application, the present application is more particularly directed to specific forms of vibrator-translator elements, and associated circuits, which provide greater voltage variation for a given mechanical movement, and have other attendant advantages. Merely as a suggestive term, and without intending to impose any limitations thereby, the present application may be considered as directed to push-pull operation. That is, layers on opposite sides of the vibrator-translator element have their impedance varied simultaneously but oppositely by vibration of the element, these layers being serially connected to provide a connection at their inner or mutually connected ends and at their outer or other ends. While these three connections may be arranged in conventional pushpull fashion by connecting the energizing voltage to the center connection and to the center tap 01' a transformer and the outer ends of the layers to the outer ends of the transformer winding, I have found other circuit arrangements to be more advantageous. In any case, however, this "pushpull arrangement provides increased voltage variation for a given mechanical movement, balances out second harmonic distortion, and has other advantages.

Turning now more particularly to the embodiment of my invention illustrated in Figures 1 to 5, the variable resistance symbols indicated as H) and H represent strain sensitive coatings on opposite sides of the vibrator-translator element. it will be noted that these have what I am terming for convenience their inner ends connecteding tube 15 through the resistor Hi. In accordance with conventional practice the screen grid 11 of the tube isconnected to the B+ source through a voltage reducing resistor l8; the other or negative end of the plate voltage supply is' connected at some point tothe bus wire [9; and the cathode 20 of the tube is connected through a biasing resistor 2! to the bus wire 19, and directly connected to the suppressor grid 22,

V The other end of the resistance coating H is also connected to the negative bus wire [9, it being understood that this is grounded in accordance with conventional practice. The center'conidentified as It) and II) is preferably of a quarter megohm to a megohm resistance. The circuit arrangement shown in Figure 1 is particularly advantageous in that it provides a relatively high value bleeder resistor across the energizing voltage (both of the resistance portions in series), and a relatively low (only one portion) grid to ground resistance, tending to minimize oscillation and pick-up difficulties. The output of thetube I5, as may be seen, is developed between the terminals 21 and 28 across the load resistor 29, the plate lead having in series therein the couling condenser 30. A correction network may be included in the output circuit rather than the input circuit if desired.

One particular circuit which I have tested employed the following values for the circuit elements: the two portions l and II had a resistance of one-quarter megohm; the condenser 23 had a value of .05 mf.; the resistor 26 had a value of one-half megohm; the biasing resistor 2| had a value of 500 ohms; the plate resistor l6 was 100,000 ohms; the condenser 30 was .05 Inf:, and the condenser 3| was .0005 mf.; the variable resistor 32 had a maximum value of 4 megohms;

the output resistor 29 had a value of one-quarter of a megohm; the screen grid resistor I8 had a value of 350,000 ohms, the condenser 33 shunting it to ground having a value of .1 mf. The tube which I used was a; 6SJ7, the plate supply voltage being 300 volts.

Turning now more particularly to Figures 2 to 5, a vibrator-translator element adapted toprovide the desired variable resistors is shown. It

provided near the outer end to give the vibrating beam-like portion the desired vibrational characteristics. After the base of Celluloid or other material has been cut to the proper form I maskit appropriately and then spray on a coating of finely divided graphite or the like in the shapes shown, this coating making connection with rivets or other connectors at suitable points and being subsequently covered with lacquer or some other protective medium. Referring to the particular arrangement shown here, one coating extends from the rivet 39 down to the bottom edge of the side of the element shown in Figure 2, and then forwardly along this edge, this portion being identified as 40; the coating then .has a vertical portion out near the end of the needle, identified as M, running up to the upper edge of this side, then running back along this side in the portion identified as 42 to connect with the rivet A3. The coating then extends across the forward face of the rear enlarged portion, as may be best seen in Figure 5, this portion of the coating being identified as M. In order to avoid a high resistance path on the inactive base portion of the needle these portions of the coatings may be covered with silver paint or metal foil.

Now turning to Figure 4, showing the other side of the needle, it will be seen that the coating extends forwardly along the top edge of this'side of the needle, this portion being identified as 15, downwardly near the outer end of the needle in a portion identified as 36, andback along the bottom edge of the needle in a portion identified as 41 to make connection with the rivet &8. By this arrangement the coating portions A0 and 42 provide the resistance schematically identified as I0 in Figure 1, the coating portions 45- and 46 providing the resistance schematically identified as H in Figure 1, the arrangement being such tha+ lateral vibratory movement of the element (as a result of movement of the needle in the grooves of a laterally cut record) causes simultaneous but opposite variation of the resistances on the opposite sides of the translating element. The cross-over portion 44 provides the center connection between the resistance portions on opposite sides of the needle, corresponding to the leads schematically illustrated as l2 in Figure 1, the connection to the grid 25 being conveniently taken off from the rivet 43. The connections schematically illustrated as l3 and IS in Figure 1 may be conveniently taken off from the other ends of the resistance coatings by connections to the rivets 39 and 48. It will be understood that the advantages of my push-pull circuit illustrated in Figure 1 can be lator element having a coating going out one side, crossing over at the end, and coming back on the other side, as illustrated in my above-mentioned application. Such an arrangement, however, requires a flexible wire connection to the outer end of the needle; whereas by having the resistance coating follow a U-shaped path out to the end and back to the base of each side of the translator element, as here shown, all connections may be made at the fixedly mounted rear or base end of the element.

Turning now more particularly to the circuit shown in Figure 6, it will be seen that four variable resistance portions 50, 5|, 52 and 53 are provided on the vibrator-translator element, as will hereafter be more fully described. These are so arranged that they are connected in a diamond, and so that lateral vibration of the translator element causes simultaneous variation ofall four resistors, the variation of any two adjacently connected resistances being inopposite directions, the arrows on the circuit diagram being oppositely pointed to indicate this. Current from the negative terminal of the B voltage supply, here indicated as the battery 54, is supplied through the lead 55 to one corner of the resistance diamond, the other corner being connected through the lead- 56 to the positive side of this source. The other achieved by a vibrator-transtwo corners of the resistance diamond are connected to tubes arranged in push-pull relation, the upper corner (speaking with respect to Figure 6) being connected through the lead and the coupling condenser 58 to the grid 59 of the tube 60; and the bottom corner being connected through the lead 6| of the tube 64. While these tubes are shown as simple triodes for convenience of illustration, it will be understood that in practive they would be pentodes or other multi-element tubes. In accordance with conventional practice the cathode elements 65 and 66 are connected through biasing resistors 61 and 68 to the grounded negative terminal of the B supply; and the plates 69 andlu are connected to the outer ends of the primary H of a push-pull transformer, the positive side of the plate supply voltage being connected to the center tap of this primary. The secondary 12 of this same trans former is connected to the succeeding tube 13 of a single ended amplifier, one end of the secondary being connected to the grid 14 and the other end to the cathode 15 through the biasing resistor 76. As before, input load resistor 11 and 18 are employed in shunt between the grid and cathodes of each of the tubes Bil and- 64, these preferably having a resistance slightly higher than the resistance of any particular section or portion of the resistance diamond provided by the coatings or strain sensitive layers on the vibrator-translator element. The values of the various circuit constants would be approximately similar to those previously described.

Turning now more particularly to Figures 7 to 9 a form of vibrator-translator adapted to be used in the circuit shown in Figure 6 is illustrated. In this particular form the base or enlarged rear portion 80 of the element is provided with only two rivets 8i and 32. The coating may be considered as startin at the rivet 8! and running along the top edge of one side of the forward or beam-like portion of the element, as shown in Figure 7, this portion being identified as 83, then across at the end of the element in the portion identified as 85, better seen in Figure 9, and back on the other side of the element shown in Figure 8, this portion being identified as 85, and extending clear along the upper edge of the base portion to make connection with the rivet 82. Re-

ferring back to other layer or coating of the high resistance material starts at the rivet 82, extends down to the M bottom edge of this side of the element, and

along this bottom edge to the front of the element, this portion being identified as 86; then it crosses over the front end of the element in the portion identified a 81, better seen in Figure 9, and runs back along the bottom edge of the side shown in Figure 8, as the portion identified as 88, to make connection with the other side of the rivet\8|.

The two terminals provided by therivets 8i and 82 may, for example, be used as the corners of the resistance diamond connected to the voltwhereas the grid connections may e supp y; be provided by pigtails or flexible wires 89 and 90 at the outer end of the needle. As compared with a simple vibrator-translator having a resistance coating on only one side, the push-pull arrangement first described provides double the voltage variation for a given translator element fiexure, and the arrangement last described above provides four times the voltage variation for the same movement of the end of the element. Without the push-pull arrangement it has been neces- Figure '7, it will be seen that ansary, in some cases, to use a preamplifier because of the small voltage variation; but with either of the above described push-pull arrangements sufiicient voltage variation can be secured to dispense with the necessity of a preamplifier.

Push-pull arrangement of the strain sensitive coatings is also highly desirable in that it balances out sensitivity variations arising from what may be termed initial or averagecompression of the coating. The sensitivity per unit deflection is decreased where the coating was under compression before its flexure strain, and increases where it was stretched. Resistance pick-ups using only a single coating have showed variations in response to a single continued tone where the deflection did not start from zero position, as where the coating i initially compressed or expanded because of tone arm lag or an off-center record, this objection being completely eliminated by the push-pull arrangement.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

Iclaim:

1. Reproducing apparatus of the character described, including: a tone arm; a single beamlike vibrator-translator element of insulating material rigidly mounted in the tone arm at one end and having on opposite sides thereof and connected at one end coatings of material having its resistance varied by strain, whereby the resistance'of the coatings is simultaneously but oppositely varied by vibratory movement of the element; a stylus directly connected to the other end of the element for vibrating it in accordance with mechanical variations in the record being reproduced; and a circuit connected to the Junetion and outer ends of the coatings and adapted to develop voltage variations as a result of said resistance variations, the efiect of the resistance variations in said coatings being additive for the desired vibrations.

2. Vibration-translating apparatus of the character described, including: a translating element having two serially connected portions adapted to have their impedance simultaneously but oppositely varied in accordance with variations in the record being reproduced; an amplifying tube ineluding arid and cathode elements; a source of voltage connected across the outer ends of said portions; and connections from the central connection between said portions to one of the tube elements and from an outer end to the other tube element, said connections having low impedance at high frequencies.

3. Vibration-translating apparatus of the character described, including: a translating element having two serially connected portionsof high resistance adapted to have their resistance simultaneously but oppositely varied in accordance with the, vibrations being translated; an amplifying tube including grid and cathode elements; a source of voltage connected across the outer ends of said portions; and connections fromthecentral connection between said portions to one of the tube elements and from an outer end to the other tube element, said connections having low impedance at high-frequencies.

4. Reproducing apparatus of the character described, including: a tone arm; a beam-like vibrator-translator element rigidly mounted in the tone arm atone end and having on opposite sides thereof and connected at one end coatings of high resistance material having its resistance end to the other tube element.

5. Vibration-translating apparatus of the character described, including: a translating element havingfourportionsconnected in a diamond, these portionsbeing adapted to have their respective impedances varied simultaneously in accordance with the vibrations being translated, the arrangementbeing such that any two adjacent impedances vary oppositely; a source of Voltage connected to two of the corners of the diamond; and a circuit connected to the other two corners of the diamond and adapted to have voltage variations developed therein.

6. Apparatus of the character claimed in claim 5, wherein said portions are layers, on a vibratory element, of material having its impedance varied by strain.

7. Apparatus of the character claimed in claim 5, wherein the translating element is a beam-like member having two independent coatings, on each of two opposite surfaces, of high resistance material having its resistance varied by strain.

8. A vibration-translating element comprising a beam-like member of insulating material having a low coefiicient of elasticity, the member having on each of two opposite surfaces thereof a coating of high resistance material having its resistance varied by strain, this coating extending from one end of the beam-like element to the other and back again oneach side thereof, whereby all of the terminal connections are made at one end of said element.

9. A vibration-translating element comprising a beam-like member of insulating material having a low coefiicient of elasticity, the member having on each of two opposite surfaces thereof separate coatings of high resistance material having its resistance varied by strain, each of these separate coatings on each side connecting at both ends to the ends of a coating on the other side of the element, whereby four resistance portions are provided, the connections between the ends of these portions being in the form of a diamond.

KENNETH J. GERMESHAUSEN. 

